Giant infected splenic pseudocyst complicated by rupture in a patient with chronic Q fever

Abstract

Giant infected splenic pseudocysts are rare and may be difficult to diagnose due to overlapping clinical and imaging features with other cystic splenic lesions, including hydatid cysts and abscesses. At our institution, a 59-year-old male with no reported history of splenic trauma presented with weight loss, early satiety, and left upper quadrant pain. Computed tomography demonstrated a large calcified splenic cyst measuring up to 14.6 cm with internal septations and an air-fluid level, concerning for infection and rupture. The cyst fluid measured a median of 12 Hounsfield units, without perceptible wall or septal enhancement. Ultrasound demonstrated complex internal debris and septations without internal vascularity. Serologic testing showed markedly elevated Coxiella burnetii titers, and splenic tissue polymerase chain reaction testing was positive. The patient underwent pre-operative splenic artery embolization followed by open splenectomy. Intra-operatively, the cyst ruptured with the release of purulent material without fistulous communication. The postoperative course was complicated by a pancreatic leak and a subsequently identified transverse colonic defect, managed with segmental colectomy and end colostomy. Histopathology demonstrated a fibrous cyst wall without epithelial lining, consistent with a pseudocyst. This case expands the recognized spectrum of complicated splenic pseudocysts, with rupture and polymicrobial superinfection occurring in the setting of concordant serologic and molecular evidence of C burnetii.

Introduction

Splenic cysts are uncommon lesions of the spleen, with an estimated incidence of approximately 0.5%-2% in the general population, most frequently detected incidentally during abdominal imaging performed for unrelated indications [1]. Despite their rarity, the increasing use of cross-sectional imaging modalities such as computed tomography (CT) and ultrasound has led to greater recognition of these lesions in recent years [2]. Splenic cysts encompass a heterogeneous group of entities that can be broadly categorized as primary (true) cysts or secondary (false) cysts, based on the presence or absence of an epithelial lining [3].

Primary splenic cysts are relatively rare and include parasitic and nonparasitic cysts. Parasitic cysts, commonly caused by Echinococcus granulosus, account for the majority of true splenic cysts worldwide, particularly in endemic regions [1]. Nonparasitic primary cysts, including congenital epidermoid and dermoid cysts, are less common and are thought to arise from mesothelial or epithelial inclusions within splenic tissue during embryologic development. Secondary cysts, also known as pseudocysts, lack an epithelial lining and typically develop following splenic trauma, infarction, or infection, and represent the majority of splenic cysts encountered in clinical practice [4].

Although many splenic cysts remain asymptomatic, larger lesions may produce symptoms due to mass effect, including left upper quadrant abdominal pain, early satiety, nausea, or abdominal distension. Complications such as infection, hemorrhage, rupture, or fistulization are rare but may necessitate surgical intervention [5]. Imaging plays a critical role in the initial detection, characterization, and management planning of splenic cystic lesions. CT and ultrasound can typically identify features such as wall calcification, septations, internal debris, or air-fluid levels, which help narrow the differential diagnosis.

Despite the wide range of splenic cyst etiologies described in the literature, large complex splenic cysts with calcification and internal air-fluid levels remain rare and raise concern for infection, post-traumatic pseudocyst, or less common cystic splenic lesions [4]. Management strategies vary depending on cyst size, symptomatology, and complexity, with larger or symptomatic lesions often requiring surgical intervention, including surgical decapsulation, fenestration, and partial or total splenectomy [5,6].

Chronic Q fever is an uncommon zoonotic infection caused by Coxiella burnetii that most commonly involves endocardial or vascular structures [7]. Splenic manifestations, including abscess formation or rupture, are rare [6,8], and a causal association with a pre-existing splenic cyst has not been established.

Given the rarity of these presentations, individual case reports continue to provide valuable insight into their imaging characteristics, diagnostic considerations, and management strategies. Here, the case of a large complex calcified splenic pseudocyst complicated by superimposed infection and rupture in a patient with serologic and molecular evidence of chronic Q fever is presented, highlighting the diagnostic challenges and clinical management of these uncommon entities.

Case report

A 59-year-old male initially presented with several months of progressive weight loss, early satiety, and intermittent left upper quadrant abdominal pain. The patient reported an unintentional weight loss of 30-40 pounds over several weeks. He endorsed night sweats and lightheadedness but denied nausea, fever, or respiratory symptoms. Review of the patient’s social history did not identify any documented zoonotic or occupational exposure risk factors.

Initial laboratory studies demonstrated anemia (hemoglobin 7.6 g/dL), marked leukocytosis (23.1 × 10³/µL) with neutrophilic predominance (85.6%), and marked thrombocytosis (1421 × 10³/µL). Given persistent symptoms, a baseline chest radiograph (Fig. 1) was obtained, demonstrating elevation of the left hemidiaphragm with an adjacent left upper quadrant air-fluid level, initially mimicking a prominent gastric bubble. Subsequently, contrast-enhanced CT of the abdomen and pelvis (Fig. 2) demonstrated a large complex cystic splenic lesion occupying most of the splenic parenchyma and measuring 11.2 × 14.6 × 13.4 cm. The cyst fluid measured a median of 12 Hounsfield units (HU). The lesion had a relatively thin, circumferentially calcified wall and internal calcified septations, without perceptible wall or septal enhancement. A prominent air-fluid level was present, and the lesion caused mass effect on the stomach and left kidney. There was a punctate discontinuity at the periphery of the cyst with multifocal pockets of extraluminal air, concerning for intraperitoneal rupture. This prompted subsequent CT imaging with oral contrast. CT with oral contrast suggested possible communication between the cyst cavity and adjacent gastrointestinal structures, prompting concern for hollow viscus perforation or fistulization.

Fig. 1.

Initial frontal chest radiograph obtained in the emergency department demonstrates elevation of the left hemidiaphragm with an adjacent left upper quadrant air-fluid level.

Fig. 2.

Contrast-enhanced CT of the abdomen and pelvis. Axial imaging demonstrates a large splenic cyst with a thin, circumferentially calcified wall and an air-fluid level (A). Coronal images demonstrate focal discontinuity of the calcified wall (red arrow) (B) and internal calcified septations (yellow arrow) (C). Postoperative coronal CT demonstrates pneumoperitoneum and a loculated air-fluid collection (asterisk) in the splenectomy bed with surgical drains in place (D).

Subsequent abdominal ultrasound demonstrated a large complex splenic cyst with heterogeneous low-level internal echoes or debris and internal septations. The calcified wall produced posterior acoustic shadowing that limited complete sonographic characterization. Color Doppler showed no internal or septal vascularity. The lesion remained better characterized on CT, and MRI was not performed. The patient reported no history of splenic trauma. Review of scout imaging from 16 years before this visit incidentally demonstrated that rim calcification had been present in the left upper quadrant, supporting a long-standing process with concern for superimposed infection. Echinococcal serology was negative. Given the size of the lesion and concern for possible infection or neoplasm, the patient was admitted for further evaluation and management. During hospitalization, an extensive infectious workup was initiated. Serologic testing demonstrated markedly elevated Q fever IgG titers (Phase I IgG 1:2048; Phase II IgG 1:1024), and polymerase chain reaction testing of splenic tissue subsequently returned positive for C burnetii, raising suspicion for chronic Q fever as a possible contributing infectious etiology. These findings supported potential splenic involvement but did not establish that C burnetii caused the cyst or its superinfection. Given the association of chronic Q fever with infective endocarditis, both transthoracic and transesophageal echocardiography were performed and demonstrated no valvular vegetations or evidence of endocarditis. Empiric antimicrobial therapy with ceftriaxone and metronidazole was initiated, with adjunctive albendazole added for empiric antiparasitic coverage. Following microbiologic confirmation of C burnetii, antimicrobial therapy was transitioned to doxycycline-based therapy for treatment of chronic Q fever. Definitive splenectomy was planned.

The patient underwent preoperative splenic artery embolization due to the large size of the lesion and concern for intraoperative bleeding risk. Angiography demonstrated a large partially calcified splenic mass with associated arterial supply from splenic arterial branches, as shown in Figure 3A. Distal interlobar splenic arterial branches were embolized with five 10-mm Cook Nester coils, three 3- × 3.3-mm VortX Diamond coils, and two 14-mm × 50-cm Embold fibered coils. Complete stasis and near-complete splenic artery occlusion were achieved, with no immediate complication (Fig. 3B). The following day, the patient underwent a total splenectomy. Intraoperatively, the spleen contained a large complex cyst densely adherent to the stomach, splenic flexure, pancreatic tail, diaphragm, and adjacent retroperitoneal structures. During surgical dissection, the cyst was noted to have ruptured with the release of purulent material. No fistulous communication with adjacent gastrointestinal structures was identified. Due to dense adherence, a partial distal pancreatectomy was performed during dissection.

Fig. 3.

Splenic angiography demonstrates a partially calcified hilar mass supplied by splenic arterial branches (A). Postembolization angiography demonstrates complete stasis after coil embolization of distal interlobar branches (B). No immediate embolization complication was documented.

On postoperative day 6 after the operation, the patient developed worsening tachycardia, leukocytosis, and septic shock requiring intensive care. Repeat CT demonstrated a large air-fluid level at the surgical site with a new left-sided pleural effusion. The surgically placed drains from the index operation, positioned within the splenectomy bed and adjacent to the distal pancreatic resection bed, were noted to have feculent output, raising concern for an enteric leak. An additional CT of the abdomen and pelvis was then performed, revealing extravasation of contrast at the splenic flexure. The patient returned to the operating room for washout and exploration, where the surgical team discovered a 1-cm hole along the antimesenteric side of the distal transverse colon with feculent spillage, an extensive fibrinous rind throughout the peritoneal cavity, and mild saponification adjacent to the transverse colon. Subsequent evaluation identified a transverse colonic defect after the index operation, without evidence of a pre-existing colosplenic fistula. There was no intraoperative evidence of fistulization to the stomach. The greater curvature was intact and remained air-tight during submersion testing. The surgical team then performed a segmental transverse colonic resection and end colostomy. The postoperative course was also complicated by a pancreatic leak managed with drains. The patient recovered well from this second operation and was discharged from inpatient hospital care with surgical drains in place. At follow-up clinic appointment about 4 weeks after the take-back operation, moderate-volume necrotic pancreatic fluid was noted in the surgical drains without evidence of feculent material.

Gross pathologic examination revealed a disrupted spleen, consistent with intraoperative reports of rupture. The spleen was notably enlarged, in aggregate measuring 844.9 g (normal: 150-200 g) and 18.5 cm in greatest dimension (normal: 7-14 cm in length), with fragments of possible fibrous cyst wall, hemorrhage, calcification, and focal necrosis (Fig. 4). Histopathologic evaluation of hematoxylin and eosin-stained slides showed inflammation, giant cell reaction, necrosis, and cholesterol clefts. No epithelial lining was identified, and histologic examination showed neither fibrin-ring granulomas suggestive of C burnetii infection nor an echinococcal cyst wall or parasitic elements. Splenic abscess culture grew Streptococcus anginosus with mixed enteric and anaerobic flora. Overall, these findings were most consistent with a splenic pseudocyst with superimposed polymicrobial infection (Fig. 5, Fig. 6).

Fig. 4.

Gross photograph of the spleen demonstrating disrupted fragments (*), consistent with reports of rupture, with possible cyst wall, areas of hemorrhage, and calcification (⇒). Note that this photograph was taken following some sectioning in the pathology lab. In aggregate, the specimen measured 844.9 g (normal: 150-200 g) and 18.5 × 17.5 × 8.5 cm (normal: 7-14 cm in length).

Fig. 5.

Low-power histology of spleen. Low power histopathologic evaluation shows extensive areas of necrosis (⇡), along with inflammation (⇗) and calcifications (↑). No epithelial linings are seen. Relatively uninvolved splenic parenchyma is present (bottom) with focal hemorrhage (*).

Fig. 6.

High-power histology of spleen. High power histopathologic evaluation demonstrates cholesterol clefts (⇖), multinucleated giant cells (↑), and other inflammatory cells (*). No fibrin ring granulomas were identified. The overall pathologic findings are most consistent with a splenic pseudocyst.

Discussion

Splenic cysts are uncommon lesions with a broad differential diagnosis that includes: congenital epithelial cysts, parasitic cysts, post-traumatic pseudocysts, chronic hematomas, abscesses, and cystic neoplasms. Among nonparasitic splenic cysts, pseudocysts are the most frequently encountered subtype and are defined histologically by the absence of an epithelial lining. They are generally thought to arise following trauma, infarction, or infection, with subsequent encapsulation of liquefied material by fibrous tissue [9]. Although many remain asymptomatic and are discovered incidentally, larger lesions may produce abdominal pain and mass effect. Complicated lesions may present with rupture or hemorrhage [5]. The current case is notable not only for its giant size and chronic calcification, but also for its rupture and highly unusual association with a chronic C burnetii infection.

From a radiologic perspective, several imaging findings in this case were highly suggestive of a chronic complicated splenic pseudocyst. Thick peripheral calcification, internal septations, and long-term persistence on prior imaging favored a chronic pseudocyst, although no antecedent trauma was reported. Median fluid attenuation of 12 HU, absence of wall or septal enhancement, and absence of internal Doppler vascularity supported a complex cystic lesion. In addition, the presence of a large air-fluid level and wall discontinuity strongly raised concern for superimposed infection and rupture. CT remains the most useful modality for assessing these features, particularly when evaluating internal gas and mass effect on nearby organs [10]. Ultrasound can further characterize internal echogenic debris and complexity, but is generally less specific than CT for evaluating rupture or fistulous complications. MRI may help characterize hemorrhagic or proteinaceous contents and enhancing soft-tissue components when CT and ultrasound are indeterminate, but MRI was not performed in this case. Superimposed abscess was supported by internal gas, debris, and positive cultures, whereas hydatid disease was less likely because serology was negative and no daughter cysts or parasitic elements were identified. A primary epithelial cyst was excluded histologically, and cystic neoplasm was less likely because there was no enhancing solid component or internal vascularity [[2], [3], [4], [5],9,10].

An important diagnostic issue in this case was the possibility of fistulous communication to the gastrointestinal tract. Fistulization of splenic cysts to the gastrointestinal tract is an extremely rare complication, with the most common types being gastrosplenic and colosplenic fistulas. These fistulas are thought to occur through mechanisms distinct from simple cystic formation, typically involving chronic inflammation, pressure necrosis, or underlying malignancy.

In addition, gastrosplenic fistulas are most commonly attributed to malignant processes, particularly lymphoma, but have also been described in association with peptic ulcer disease and splenic abscess. In these cases, the fistulous tract most often forms between the greater curvature or fundus of the stomach and the spleen or splenic vasculature, as was initially suspected in the present case [11,12]. Colosplenic fistulas are even more rare and are primarily associated with malignancy or severe inflammatory processes involving the colon [13].

Radiologically, the presence of gas within a splenic lesion may mimic abscess or infection alone and, on a chest radiograph, may be mistaken for a prominent gastric bubble because of its left upper quadrant air-fluid level configuration. CT plays a critical role in identifying subtle communication with adjacent bowel, surrounding inflammatory changes, and potential hemorrhagic complications. However, imaging findings suggestive of fistulization may instead reflect dense adhesions and rupture-related inflammation rather than a true pre-existing fistula. In this case, CT with oral contrast suggested communication with adjacent bowel, but no fistulous tract was found during splenectomy, and subsequent gastric leak testing was negative. The later colonic contrast extravasation corresponded to a 1-cm transverse colonic defect identified at reoperation. Thus, neither a pre-existing gastrosplenic nor colosplenic fistula was confirmed. The initial intralesional gas occurred in the setting of superimposed infection and suspected rupture, whereas the colonic leak developed postoperatively.

Another unusual feature of this case is the association with chronic Q fever. C burnetii is an obligate intracellular gram-negative organism that most commonly causes either an acute febrile illness or a chronic infection involving the endocardium or vascular structures. Chronic Q fever most often manifests as endocarditis or vascular infection, whereas splenic involvement is distinctly uncommon [7]. Although not specific to Q fever, contemporary literature on infected native aortic aneurysms similarly emphasizes microbiologic variability and the importance of integrating imaging with clinical and laboratory findings [14,15]. Splenic abscesses and spontaneous splenic rupture have been reported but remain rare [6,8]. In this patient, elevated phase I IgG titers and positive splenic tissue PCR supported possible splenic involvement by C burnetii. However, detection of C burnetii DNA in splenic tissue does not establish that the organism caused the long-standing cyst or its acute infection. Histopathology did not demonstrate fibrin-ring granulomas, whereas cultures demonstrated S anginosus with mixed enteric and anaerobic flora, supporting polymicrobial superinfection. Thus, C burnetii remains a potential contributor to the splenic process rather than an established cause.

The mechanism by which C burnetii could involve a chronic splenic pseudocyst is uncertain. One possibility is hematogenous seeding of a long-standing devitalized cavity with poor immune clearance. Another is that chronic inflammation and structural instability predisposed the cyst to secondary infection. The lesion in this case had been present for at least 16 years before clinical deterioration, supporting the interpretation that infection was superimposed on a pre-existing pseudocyst rather than being the primary initiating event.

Management of giant splenic pseudocysts depends on lesion size, symptoms, and complexity. Small asymptomatic cysts may be observed, but large or symptomatic lesions and those with complications typically require intervention. While spleen-preserving approaches may be considered in select cases, total splenectomy is often preferred for large, hilar, or densely adherent lesions [5]. In this case, the size of the lesion, extensive adhesions, and concern for infection made splenectomy the most appropriate definitive treatment. Preoperative splenic artery embolization also played an important role in management. Embolization can reduce splenic perfusion and intraoperative blood loss, particularly in large or technically challenging lesions [2]. In this case, embolization facilitated surgical resection in the setting of a massive, inflamed, and adherent lesion.

Conclusion

This case describes a giant chronic splenic pseudocyst complicated by rupture and superimposed polymicrobial infection in a patient with serologic and tissue PCR evidence of C burnetii. It highlights the importance of recognizing imaging features suggestive of complex splenic cysts, including internal septations and air-fluid levels, which may indicate infection or rupture. Although fistulization to adjacent gastrointestinal structures remains an important diagnostic consideration in the presence of intralesional gas, imaging findings may instead reflect rupture with secondary inflammation or delayed bowel injury. This case also expands the spectrum of reported splenic manifestations associated with Q fever and underscores the importance of maintaining a broad differential diagnosis, including atypical infectious etiologies, in complex cystic splenic lesions. Ultimately, no pre-existing gastrointestinal fistula was confirmed. A transverse colonic leak was identified postoperatively and managed at reoperation. Early multidisciplinary management, including imaging evaluation, surgical intervention, and targeted antimicrobial therapy, remains essential for optimizing outcomes in these challenging cases.

Patient consent

Written informed consent for the publication of this case report was obtained from the patient.